Several of my Xbox 360 Plug & Charge Kits aren't holding charges anymore—they will turn on and connect if linked with the wire/cord/cable, but will turn off once the cord is unplugged. This happened suddenly—it's not like the battery capacity slowly drained over time.

I had noticed in the past that certain batteries work with the gray cable (from the original kits) and not the black (later version), or vice versa. E.g., a black battery will connect and charge with a black cable, the indicator light turning red after a short delay, and then to green after a few minutes. That battery will appear to stay on when unplugged and the dashboard will show the battery as full, but it'll turn off abruptly after a half hour or so. If I use a gray cable to charge the same battery, the controller turns off immediately after unplugging. I'd like to be able to use cables between batteries interchangeably, if possible.

I'm not seeing much useful feedback on other forums, though this issue seems relatively common. What is happening here? Are the original gray and black kits incompatible? Is the battery close to complete depletion and uselessness? What are the indicators of total depletion? I saw some videos on YouTube about artificially draining the battery—would that help? Is there some catch-all solution to this issue?

I'm only putting this as a comment because this is my personal experience, not fully researched. I can personally use whichever cord (gray / black) with either one of my white or black battery packs to give it power. However, the original white battery pack lasted way longer than the black one for life. The white would charge and hold it for about a year or two, when the black kit only worked for about 3 - 4 months.
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leetyOct 11 '12 at 13:26

It's a common effect with recharchable battery packs. I hope this article will provide you some insight.
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StrikeNov 16 '12 at 10:15

Is it at all possible to summarize the video as part of your answer? We would prefer not to have the bulk of your answer as part of a video that could be removed or made private
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PeterLNov 14 '12 at 13:53

The video recommends using a paperclip? SERIOUSLY? That's very dangerous. DON'T DO THAT. Use a resistor of a least 3k Ohm! It will limit the current to non dangerous levels. That will further result in taking a few hours to discharge (use some sticky tape), but it will prevent the battery pack from blowing up in your face and the paperclip from starting to smoke or melt.
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StrikeNov 16 '12 at 10:06

These batteries don't possess much potential in the danger field of using a paperclip, It's two AA equivalent batteries inside a protective case.
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fraviaseekerNov 17 '12 at 5:45

@fraviaseeker I know that they just have a maximum voltage of 3V, but with a papaerclip, which has near 0 Ohm resitance, the current goes extremely high. Even though it might not exactly blow up, the battery pack can still suffer damage that way, as well as the person doing this, as the paperclip will get extremely hot in less than a second. Hence the warning of smoking and melting.
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StrikeNov 17 '12 at 16:19